Piercing tool for the piercing of large metal blocks

ABSTRACT

A piercing tool for piercing holes in large metal blocks comprising two distinct members. The shaft transmitting to the tool the force of the piercing press has rigidly secured and axially aligned to its end an axial member of smaller diameter than the shaft. A ring-shaped member having a diameter equal to that of the hole to be formed is annularly positioned about the axial member and is detachably mounted to the assembly made up of the shaft and axial member. After the hole has been pierced, the ring-shaped member is detached from that assembly as the tool is withdrawn through the hole in the metal billet.

United States Patent Inventors Appl. No. Filed Patented Assignee Priority PIERCING TOOL FOR THE PIERCING OF LARGE Primary Examiner-Charles W. Lanham Assistant ExaminerR. M. Rogers Attorney-Webb, Burden, Robinson & Webb ABSTRACT: A piercing tool for piercing holes in large metal blocks comprising two distinct members. The shaft transmitting to the tool the force of the piercing press has rigidly secured and axially aligned to its end an axial member of smaller diameter than the shaft. A ring-shaped member having a diameter equal to that of the hole to be formed is annularly positioned about the axial member and is detachably mounted to the assembly made up of the shaft and axial member. After the hole has been pierced, the ring-shaped member is detached from that assembly as the tool is withdrawn through the hole in the metal billet.

METAL BLOCKS 4 Claims, 3 Drawing Figs.

[1.8. Ci 72/43, 72/327, 72/273 Int. Cl ..B21b 45/02, B2lb 31/02 Field of Search 72/254, 256, 273, 43, 327

lo a 9 I, I\\ 4 T PATENTED JUN I 1971 Fig.5

1 Fig.2

0 w mw m THE/R ATTORNEYS PIERCING TOOL FOR THE PIERCING OF LARGE METAL BLOCKS This invention relates to a piercing tool and more particularly to a piercing tool which is used for forming accurately positioned holes in large metal workpieces such as metal billets.

Many operations used in industry today require heavy metal billets having large strictly coaxial holes. For example, such billets are often used in the manufacture of pipe by various techniques. A common method for piercing such large workpieces involves placing one of them such as a large square or cylindrical workpiece in the container of a press and compressing it into close contact with the container wall.

A piercing tool is then forced by the press to penetrate axially into the workpiece, ultimately traveling completely through it and carrying along with it a small portion of the workpiece, hereinafter referred to as the plug.

This procedure does not always guarantee a sufficiently precise coaxiality between the hole in the billet and the outer surface of the billet especially where the length of the hole is large with respect to its diameter. In such cases, a process generally known as expansion" is employed. This process, described in French Pat. No. 1,130,759, involves boring a pilot hole of small diameter into the block by cold machining. The pilot hole is positioned precisely coaxially with respect to the metal billet and its entry is flared. The metal billet is then raised to its temperature of deformation (if appropriate), placed in a container of a piercing press and a lubricant is applied to the pilot hole. A piercing tool, having a leading end of a diameter slightly smaller than that of the pilot hole and an enlarged portion adjacent the leading end (often connected to the leading end by a truncated cone member), is guided through the pilot hole by the leading end and forced to penetrate the billet to form a bore of the same diameter as that of the enlarged portion.

In all these processes the largest cross section of the piercing tool defines the interior cross section of the bore to be obtained. Moreover, after passing through the billet, the piercing tool is not retracted together with the mandrel or shaft through which the force of the press is transmitted to the tool. The tool itself remains connected to the plug and, therefore, it must be separated from the shaft. Therefore, the connection between the shaft and the tool must be of sufficient strength to keep the tool connected to the shaft while the equipment is being set in place and during piercing but must also be sufficiently fragile to enable the tool to break away from the shaft after piercing is completed when the shaft begins to be retracted. In practice, such connections are made by springs, circular clips, atmospheric depression etc-as is well known in the art.

The difficulty in separating the piercing tool from the plug which adhere to one another over a large contact surface is a significant drawback to these processes. The deterioration of the tool caused by the separation often requires scrapping the entire tool and prevents its reuse. The difficulty is increased as the diameter of the tool is increased.

In addition, the greater the diameter of the hole desired, the larger and heavier the tool required. Such large tools are difficult to manipulate and the cost of their manufacture taken with the limitations on their reuse substantially increase the production costs of the operation.

Finally, in the known processes, it is necessary to ensure lubrication between the working surface of the tool and the surface being formed in the billet. In operations at more than 500 C. a vitreous material is often used for this purpose. When starting with a solid billet, a reserve supply of vitreous material is placed between the face of the block and the front face of the tool. Sometimes the front ofthe tool is given a concave shape to form a space between the billet and the tool for the reserve lubricant as described in French Pat. No. 1,043,869. If the billet has a prebored pilot hole, the lubricant can be placed in the hole as taught by French Pat. No. 1,130,759. However, neither method is completely effective to guarantee a uniform distribution of the lubricant when the desired final bores have diameters larger than 5 inches, as is the case when presses with a great force are used.

Our invention overcomes these difficulties. It provides a piercing tool in which the difficulty encountered in separating the tool from the plug is decreased. The weight of the portion of the piercing tool that is subjected to wear and which has to be manipulated before each operation is reduced. And in cases where the metal billet has been already bored, our invention guarantees uniformity of lubrication.

Briefly stated, our invention is a piercing tool made up of two distinctly separate members, it is affixed to a mandrel or shaft. An axial member is rigidly and axially secured to one end of the shaft and a ring-shaped member is detachably secured about the axial member and adjacent to the shaft.

In the accompanying drawings, we have shown our presently preferred embodiments of our invention in which:

FIG. 1 is a section through a piercing press equipped with our piercing tool for use with a billet which has been previously cold bored,

FIG. 2 is a closeup in section of the piercing tool of FIG. 1; and,

FIG. 3 is a section of our piercing tool for use with a metal billet which has not been earlier bored.

With reference to FIG. 1, the piercing press has a container 1 in which the metal billet 4 is positioned. The metal billet 4 rests on a base 2 of the press which has an opening in alignment with the part of the billet through which the piercing tool passes. The billet 4 in FIG. 1 has a previously bored hole 8 of appreciably smaller diameter than the ultimate desired size.

The piercing tool itself which is acted upon by the press (not shown) through the mandrel or shaft 3, comprises an axial member 5 and a ring-shaped member 6. The axial member 5, which is of a smaller diameter than the shaft 3, is rigidly and axially secured to the end of shaft 3 such as by threading as shown in FIG. 1. The axial member 5 has a downwardly extending protuberance 9 which acts as a guide in the previously bored opening 8. The ring-shaped member 6 is annularly disposed and detachably mounted about axial member 5 and in contact with the bottom of shaft 3. Of course, the largest outside diameter of ring-shaped member 6 represents the diameter of the hole to be obtained. The connecting means 7 between ring-shaped member 6 and either axial member 5 or shaft 3 can be ofa variety of kinds well known in the art, for example, the previously mentioned spring, circular clip or atmospheric depression assemblies. These connecting means are positioned on the surface of contact between ring-shaped member 6 and either axial member 5 or shaft 3. A portion of the surface of axial member 5 is conical and melts into protuberance 9. This conical surface is aligned with a chamfered leading edge or the ring-shaped member 6 and defines with it a ring-shaped recess 10, as shown in FIG. 2 between the dotted line, the lower face of the ring-shaped. member 6 and cylindrical lateral surface of the axial member 5. This recess 10 is filled up at the beginning of the operation by the lubricating material placed in the flared entry of the pilot hole and constitutes a reserve supply providing a sufficient and uniform lubrication during piercing. For this purpose, the entry face of the pilot hole is flared to a diameter slightly larger than that of the leading face of the ring-shaped member 6.

Another embodiment of our invention is shown in FIG. 3 where components similar to those of FIGS. 1 and 2 are identified by the same numeral followed by a prime. In FIG. 3 the metal billet 4 to be pierced is solid and there is no prebored opening as in FIGS. 1 and 2. The axial member 5 which is rigidly affixed to the bottom of shaft 3' as in the earlier embodiment has a concave leading surface in alignment with the concave leading surface of ring-shaped member 6' which is detachably mounted by connecting means 7 to axial member 5'. This concave surface forms a recess 10 between the tool and the metal workpiece 4', which provides a place for the reserve supply of lubricant, as taught in the case of sin gle block tools by US. Pat. No. 2,756,494.

In both embodiments of our invention, the outer diameter of ring-shaped member 6 or 6 is larger than shaft 3 or 3'. After the piercing is completed, the replaceable ring-shaped member 6 or 6 is detached from the shaft 3 or 3 when axial member 5 or 5 is withdrawn together with shaft 3 or 3 through the pierced opening. The ring-shaped member 6 or 6' may then be replaced by a new ring-shaped member prior to the next piercing operation.

Finally, the plug adheres only to the ring-shaped member 6 or 6. Consequently, the adherence is weaker than if the plug adhered to the entire contact surface between the whole piercing tool and plug. Wear is exerted principally on the lateral surface of the ring-shaped member and consequently on a part less heavy and less expensive than in the known process. Although some wear can be exerted on the lateral surface of axial member 5 of the embodiment shown in FIG. 2, the wear has no harmful effect on successive operations since the ultimate cross section of the bore is determined by the diameter of ring-shaped member 6.

EXAMPLE Our invention has been used successfully as follows: A piercing press with a force of 2,300 tons equipped with a container having a diameter of l3.2 inches was used to transform a hole from a cold bored diameter of 1.575 inches into a 6.3 inch hole by meansof hot forming at 2,l F. employing a vitreous lubricant. The piercing tool employed was that shown in FIG. 2 wherein the diameter of the axial member 5 was about 2.160 inches. The ring-shaped member 6 which was replaced after each push weighed less than 4 pounds, whereas a single block tool, as presently known heretofore, would have weighed about 40 pounds.

While we have shown and described preferred embodiments of our invention, it may be otherwise embodied within the scope of the appended claims.

We claim:

1. A piercing tool for producing holes in metal billets and the like when forced into them by a press through a shaft comprising:

A. An axial member, axially aligned and rigidly mounted to an end of said shaft; and

B. A ring shaped member annularly and detachably mounted about said axial member and adjacent said shaft so that the ring shaped member is detached therefrom after said piercing tool has passed through the metal billet when said shaft and axial member are withdrawn, the outside diameter of said ring shaped member defining the diameter of the produced hole.

2. The piercing tool of claim 1 wherein a leading end of the axial member is concavely shaped and aligned with a concavely shaped leading end of said ring-shaped member to form a space for a lubricant between the piercing tool and the metal billet just prior to the piercing operation.

3. The piercing tool of claim 1 wherein the axial member has a forwardly extending protuberance extending beyond the end of the ring-shaped member so that the protuberance acts as a guide in a pilot hole previously bored in the billet to a diameter slightly larger than that of said protuberance.

4. The piercing tool of claim 3 wherein a portion of the lateral surface of the axial member is cylindrical and a portion is conical and in line with a conical surface of the leading part of the ring-shaped member so that an angle between the cylindrical surface of the axial member and the leading face of the ring-shaped member forms a recess where the lubricant gathers at the beginning of the operation. 

1. A piercing tool for producing holes in metal billets and the like when forced into them by a press through a shaft comprising: A. An axial member, axially aligned and rigidly mounted to an end of said shaft; and B. A ring shaped member annularly and detachably mounted about said axial member and adjacent said shaft so that the ring shaped member is detached therefrom after said piercing tool has passed through the metal billet when said shaft and axial member are withdrawn, the outside diameter of said ring shaped member defining the diameter of the produced hole.
 2. The piercing tool of claim 1 wherein a leading end of the axial member is concavely shaped and aligned with a concavely shaped leading end of said ring-shaped member to form a space for a lubricant between the piercing tool and the metal billet just prior to the piercing operation.
 3. The piercing tool of claim 1 wherein the axial member has a forwardly extending protuberance extending beyond the end of the ring-shaped member so that the protuberance acts as a guide in a pilot hole previously bored in the billet to a diameter slightly larger than that of said protuberance.
 4. The piercing tool of claim 3 wherein a portion of the lateral surface of the axial member is cylindrical and a portion is conical and in line with a conical surface of the leading part of the ring-shaped member so that an angle between the cylindrical surface of the axial member and the leading face of the ring-shaped member forms a recess where the lubricant gathers at the beginning of the operation. 